Inclosed safety-fuse.



A. L. EUSTICE.

" INCLOSED SAFETY FUSE.

APPLICATION FILED Aua.2.1915.

1,278,893. Patented sept. 17,1918.

UNITED STATES PATENT OFFICE.

ALFRED L. EUs'rIoE, or omesso, ILLINOIS.

i citizen of the United States,` residin v e the fusible lin INcLosEn SAFETY-russ.

To all whom it may concern Be it known that I, ALFRED L. EUsTIor., a

Specification of Letters Patent. Patented Sept. 17, 1918. Application mea August 2, 1915. serm1N.4s,o77.'

will'cperate much more accurately when the .fuse linkis surrounded by air than when it 1s y.surrounded by av non-conducting filling Chicago, in the county of Cook, and tate \material, while under short-circuit'tests the of Illinois, have invented certain new and useful Improvements in Inclosed Safety- Fuses, of` which the following is especification.

My invention relates to inclo'sed safety fuses used for the protection of electric circuits, and refers particularly (although not exclusively) to cartridge fuses of the nonrenewable type. f

Inclosed safety fuses are of two generall j well-known ltpesfmirst, those in whic may be renewed by the user of ,the fuse after the latter has blown,

although the same 1 fuse vcasing and other parts may beused` repeatedly, and, second,

those of" the non-renewable type. in .which the entire fuse is supposed to .be discarded after it `has blown a single time. There are advantages in each of these two general ty-pes of fuses. The renewable type utilizes the same parts, with the exception of the fusible link, many times, and thus the cost to the user foreach blow-out is greatly reduced.

-At the same time, in a properly constructed fuse of this type the lire hazard is greatly reduced over what it is when a fuse' not intended to be renewed by the user is improp erly renewed by various-crude means which ma be at the disposal of the user.

nder certaincircumstances users of inclosed fuses .desire to eliminate all possibility ofi improper renewal of the fuse by using a type of fuse which cannot be tamgered with but must be discarded after it has een blown a single time.

It is one of the ob'ects of my invention to provide an inclosedy use in which a new link cannot be inserted in the fuse without destroying the parts thereof, so that the fuse would be ino erative, while at the same time I have embo ied in my improved fuse various features of construction which cause it to operate most satisfactorily under various conditions. Among these features may be mentioned the use of a link having prefer-l ably three portions of restricted cross-sectional area therein, at least one of these portions being located in an air chamber within the fuse'casing and other restricted portions being locatedin chambers which are provided with anon-conducting filling. .It

as been found that in rating tests a fuse `volatilized .gases are more' quicklycondensed whena filling material is employed than is the case when such is absent. In cartridge fuses in which no filling material is employed it is customary to release the gases slowly through restricted vent! passages,

thereby reducing the noise, of the fuse underl short clrcuit, and aiding to prevent thev explosion of the fuse. When a fuse is made without a venting. system, however, it becomes lncreasingly important to quickly condense the gasesformed on blowing the fuse. In lthe non-renewable fuse of my present invention I have therefore employed fillf the casing of the electrical connection between the terminals after the fuse has once been blown.

These and other objects of my invention will be more readily understood by reference to the accompanying drawings, in which- Figure 1 is a sideelevation of a fuse showing a preferred embodiment of my invention;

Fig. 2 is a longitudinal section through the fuse shown in Fig. 1; l -v Fig. 3 is a longitudinal section through the fuse. shown in Fig. 1 but taken at an angle of 90o from the section shown in Fig. 2;

Fig. 4 is a transverse section taken on the line 4-4 of Fig. 2; and

' Fig. 5 is a transverse section taken on the line 5-5 of Fig. 3.

The fuse casing 10, of fiber or other suitable insulating material, is engaged at its ends by the washers 11, each of which is provided with a slot or aperture 12 for the passage therethrough of the fusible link 13, which is preferablyV flat and constructed of zinc or other suitable metal. The portions 14, 14 of the link 13 engage the outer faces of the washers 11, 11, and are continued into the portions 15, 15, which engage the outer surface of the end portions of the casing 10. A cap16 fits over each end of the casing 10,

.means for preventing the renewal through and the edge 17 of the skirt portion o f each cap is bent into a groove 18 formed 1n the outer surface of the casin 10. It will be observed that each cap 16 orces the portion 1l tightly against the outer surface of the washer 11, and also that a tight engagement is formed between the portion 15 of the link 13 and the inner surface of the skirt of the cap 16. In oider to prevent the cap 16 from rotating, and also in order to more securely anchor each end of the fusible link in position, a triangular indentation 19 is punched from the cap into the body of the casing 10 and carries with it a portion of the fusible link, as is clearly apparent in Fig. 2. In order to assist in the electrical connection between the skirt of the cap 16 and the end portion 15 of the fusible link 13, the aperture which is caused by forming the indentation 19 1s filled with solder 20.

Theinterior of the fuse casing 10 is divided by means of the partition washers 21 into three chambers, namely, a central cham- Vber 22 and two end chambers 23. The partition washers 21 are preferably constructed of hardened steel `or the like in order to be impenetrable by a drilling tool. These washers are provided with suitable slots or apertures 24 through which the fusible link 13 passes. The chambers 23 are filled with a granulated non-conducting filling material 25, of asbestos, plaster of Paris, lime, or the like, and the chamber 22 is left without filling material of any kind but is preferably provided with a spacer tube 26, of ber or other silnilar material, which engages at its ends the partition washers 21 in order to Ahold the latter in position, the filling mate- =rial 25 within the chambers 23 serving to hold the partition washers 21 against the ends of the spacer tube 26. It will be understood that Yany other method of holding these partition washers in position could be employed without departing from-the spirit of my invention.

The fusible link 13 is provided with apertures 27 and 28 therein, thereby forming in the fusible link portions of constricted cross-sectional area, so that on passage of an electric current through the link the latter will tend to melt at these constricted portions, and when the current is of suilicient amount to constitute a short circuit, the link will melt at all three constricted portions, thereby separating from the balance of the link the intermediate ortions-between the constricted portions Without volatilizing or melting said intermediate portions.

As previously pointed out, it is possible toy rate a fuse link for over-load conditions much more accurately when the link is surrounded b .air as the heat conductivity of the latter is' practically constant, whereas if the fusible link is surrounded by a nonconducting filling material'the contact of the latter with the link is very variable, and thereby varies the operation of the fuse under over-load conditions.

In my improved fuse when the latter is `subjected to over-load it melts at the constricted portion formed by the central aperture 27 for the reason that the constricted portions formed by the apertures 28 and the portions of the fuse immediately adjacent thereto are engaged by the filling material 25, which serves to conduct the heat away from the link, and thereby prevents the melting of the latter at these portions under the same circuit conditions which will cause the fuse to melt at the con- Y stricted portion formed by the 'aperture 27.

Under short-circuit conditions, on the other hand, Where the fuse is subjected instantaneously to the action of a large amount of current the link will simultaneously melt at all three of its constricted portions, the

intermediate portions of the linkbetween these constricted portions being separated from the rest of the link without volatiliza' of a casing, terminals at the ends of said casing, a partition transversely disposed within said casing whereby the latter is divided into a pair of chambers, a fusible link extending through said' chambers and between said terminals, said link having in each of said chambers a portion more readily fusible than. the rest of said link upon passage of an electric current therethrough,

and a non-conducting filling material in one but not both of said chambers.

2. In an inclosed fuse, the combination of a casing, terminals at the ends of said casing, a hardened steel partition transversely disposed within said casing and dividing the latter into a pair of chambers, a fusible link extending through said chambers and between said terminals, said link having a portion of constricted cross-sectional area within each of said chambers, and a non-conducting filling in one but not both of said chambers.

f 3. In an inclosed fuse. the combination of a casing, 'terminals at the ends of said casing, a pair of transversely disposed partitions within said casing, whereby the latter chambers and between said terminals, said link being constricted in at least two of said chambers, and a non-conducting iller in at least one but not all of said chambers, a

constriction of said link being in a chamber containing the filler.

4. In an inclosed fuse, the combination of a casing, terminals at the ends of said casing, a pair of transversely disposed hardened steel partitions within said casing, whereby the latter is divided into a cen-V tral and two end chambers, a fusible link extending through said chambers and between said terminals, said link being constricted in at least two of said chambers, and a non-conducting filler in at least one but not all of said chambers, a constriction of said link being in a chamber containing the filler.

5. In an inclosed fuse, the combination of a casing, terminals at the ends of said casing, a pair of transversely disposed partitions within said casing, whereby the latter is divided into a central and two end chambers, a fusible link extending through said chambers and between said terminals, said link being constricted in said central chamber and at least one of said end chambers, and a non-conducting filler in at least one of said end chambers but not in said central chamber, a constriction of said link being in a chamber containing the filler.

6. In an inclosed fuse, the combination of a casing, terminals at the ends of said cas-- ing, a pair of transversely disposed partitions within said casing, whereby the latter is divided into a central and two end chambers, a spacing member between said partitions, a fusible link extending through said chambers and between said terminals, said link being constricted in said central chamber and at least one of said end chambers, and a non-conducting filler in at least one of said end chambers but not in said central chamber, a constriction of said link being in a chamber containing the filler.

7. In an inclosed fuse, the combination of a casing, terminals at the ends of said case ing, a pair of transversely disposed partitions within said casing whereby the latter is divided into a central and two end chambers,'a fusible link extending through said chambers and between said terminals, said link having a portion of eonstricted crosssectional area in each of said chambers, and a non-conducting filler in each of said end chambers but not in said central chamber.

.8. In a cartridge fuse, the combination of a casing, a perforated disk at the end of said casing, a fusible link extending through said casing and said perforated disk, the end of said link being 'bent over the .outer surfaces of said disk and saidcasing, a c ap fitting over the end of said casing, said disk and the bent-over end of said link, and an indentation in said cap extending into the 

